1. Field of the Invention
The present invention relates to a thermal treatment method of thermally treating a substrate, such as a semiconductor wafer, and a thermal treatment apparatus for carrying out the same.
2. Description of the Related Art
A manufacturing processes for manufacturing semiconductor wafers (herein after referred to simply as xe2x80x9cwafersxe2x80x9d) include an annealing process, an oxidation process and a diffusing process that are carried out in a high-temperature atmosphere in a range of 1000xc2x0 C. When carrying out a thermal treatment process of this kind by a single-wafer treatment apparatus, a wafer mounted on a support table disposed in a processing chamber is heated by a heating device, such as a lamp to heat the wafer at a processing temperature, process gasses are supplied onto the surface of the wafer by a gas supply unit, such as a shower head or an injector, disposed opposite to the wafer, and the wafer is conveyed out of the processing chamber after the temperature thereof has dropped to, for example, 400xc2x0 C. or below. During periods in which the temperature of the wafer rises and drops, an inert gas atmosphere is produced in the processing chamber. An inert gas is supplied into the processing chamber during an annealing process. In those processes, the inert gas is the process gas.
In a heating stage for raising the temperature of the wafer to the processing temperature, the amount of heat absorbed by unit area of the peripheral part of the wafer is greater than that of the central part of the wafer. Therefore, the temperature of the peripheral part of the wafer rises at a rate higher than that at which the temperature of the central part rises. In a cooling stage for lowering the temperature of the wafer from the processing temperature, the amount of heat radiated from unit area of the peripheral part of the wafer is greater than that radiated by the central part of the same. Therefore, the temperature of the peripheral part of the wafer drops more rapidly than that of the central par and the peripheral part of the wafer is cooled to a temperature lower than that of the central part of the same. It is possible that crystal defects called slips are produced in the wafer when intra-surface temperature difference in the surface of the wafer is large when the temperature of the wafer is higher than about 850xc2x0 C. Such crystal defects reduces the yield of wafers.
Studies have been made to adjust the distribution of the heating amount of a heat source with respect to the direction along the radius of the wafer. Since there is a delay in the response of the temperature control operation, control is difficult and, if the delay is long, the control will affect the uniformity of temperature distribution in the surface of the wafer instead of improving the same.
The present invention has been made in view of the foregoing problems and it is therefore an object of the present invention to provide a thermal treatment method and a thermal treatment apparatus capable of reducing the intra-surface temperature difference in the surface of a wafer, i.e., workpiece, when raising or lowering the temperature of the wafer while thermally treating the wafer.
To achieve the object, the present invention provides a thermal treatment method comprising the steps of mounting a substrate on a substrate support mount disposed in a processing chamber; raising a temperature of the substrate; thermally treating the substrate by supplying a gas from a gas supply unit to the substrate; and lowering the temperature of the substrate after completion of thermally treating the substrate; in which the gas supplied from the gas supply unit to a peripheral part of the substrate and the gas supplied from the gas supply unit to a central part of the substrate are controlled to be different from each other in at least one of flow rate, heat capacity and temperature to compensate for the difference in temperature change rate between the peripheral part and the central part of the substrate in order that intra-surface temperature distribution of the substrate is uniform.
To achieve the object, the present invention also provides a thermal treatment apparatus comprising a processing vessel defining a processing chamber and provided with a substrate support mount disposed in the processing chamber; a heater for raising a temperature of a substrate mounted on the substrate support mount; and a gas supply system for supplying a gas onto a surface of the substrate disposed in the processing chamber to achieve the thermal treatment of the substrate; wherein the gas supply system has at least two gas supply sections for supplying gases with different properties to a peripheral part and a central part of the substrate, respectively.
The above and other objects, features and advantages of the present invention will become more apparent form the following description taken in connection with the accompanying drawings.